Optimization of echo amplitudes resulting from a series of 90° pulses in an inhomogeneous static field

► The rotation axis of the τ − 90°y − τ refocusing cycle is derived for inhomogeneous B0. ► Preparation of the form α−y − τ − 90°x can optimize magnetization along this axis. ► α = 24.5° maximizes echo amplitudes, α = 45° eliminate transient behavior. ► Theory is verified on a low field magnet with inhomogeneous B0.